Material Button is not calling post method function - flutter

Question

i am beginner in FLutter , i have a json that i want to send to internet by flutter
this is the json i want to send:
{
"userid": 41,
"name": "dhya",
"price": 11,
"players": [
{
"id":1,
"firstname":"aa",
"lastname":"ee",
"position":"df",
"price":12.1,
"appearences":2,
"goals":1,
"assists":1,
"cleansheets":1,
"redcards":1,
"yellowcards":1,
"image":"qq"
},
{
"id":2,
"firstname":"aa",
"lastname":"ee",
"position":"df",
"price":12.1,
"appearences":2,
"goals":1,
"assists":1,
"cleansheets":1,
"redcards":1,
"yellowcards":1,
"image":"qq"
}
]
}
As a beginner , i did not have any idea about how to send an object that the server will receive in the json format that i wanted so i used a quicktype and i created this model
// To parse this JSON data, do
//
// final clubJson = clubJsonFromJson(jsonString);
import 'dart:convert';
ClubJson clubJsonFromJson(String str) => ClubJson.fromJson(json.decode(str));
String clubJsonToJson(ClubJson data) => json.encode(data.toJson());
class ClubJson {
ClubJson({
this.userid,
this.name,
this.price,
this.players,
});
int userid;
String name;
int price;
List<Player> players;
factory ClubJson.fromJson(Map<String, dynamic> json) => ClubJson(
userid: json["userid"],
name: json["name"],
price: json["price"],
players: List<Player>.from(json["players"].map((x) => Player.fromJson(x))),
);
Map<String, dynamic> toJson() => {
"userid": userid,
"name": name,
"price": price,
"players": List<dynamic>.from(players.map((x) => x.toJson())),
};
}
class Player {
Player({
this.id,
this.firstname,
this.lastname,
this.position,
this.price,
this.appearences,
this.goals,
this.assists,
this.cleansheets,
this.redcards,
this.yellowcards,
this.image,
this.clubid,
});
int id;
String firstname;
String lastname;
String position;
double price;
int appearences;
int goals;
int assists;
int cleansheets;
int redcards;
int yellowcards;
String image;
int clubid;
factory Player.fromJson(Map<String, dynamic> json) => Player(
id: json["id"],
firstname: json["firstname"],
lastname: json["lastname"],
position: json["position"],
price: json["price"].toDouble(),
appearences: json["appearences"],
goals: json["goals"],
assists: json["assists"],
cleansheets: json["cleansheets"],
redcards: json["redcards"],
yellowcards: json["yellowcards"],
image: json["image"],
clubid: json["clubid"],
);
Map<String, dynamic> toJson() => {
"id": id,
"firstname": firstname,
"lastname": lastname,
"position": position,
"price": price,
"appearences": appearences,
"goals": goals,
"assists": assists,
"cleansheets": cleansheets,
"redcards": redcards,
"yellowcards": yellowcards,
"image": image,
"clubid": clubid,
};
}
And now in the end the only remaining step is the function that i wrote in FLutter:
Future <void> PostRequest() async {
// set up POST request arguments
final url = Uri.parse('http://localhost:3000/api/questions/addQuestion');
Map<String, String> headers = {"Content-type": "application/json"};
ClubJson club = ClubJson(userid: 1, name: "dsds", price: 55.2,players: null );
for(var item in widget.selectedPlayers){
club.players.add(Player(id:item.playerID,firstname:item.firstName,lastname:item.lastName,position:item.position,price:item.price,appearences:item.appearances,goals:item.goals,assists:item.assists,cleansheets:item.cleanSheets,redcards:item.redCards,yellowcards:item.yellowCards,image:item.image));
}
String json = club.toJson().toString();
print(club);
// make POST request
Response response = await post(url, headers: headers, body: json);
// check the status code for the result
int statusCode = response.statusCode;
// this API passes back the id of the new item added to the body
String body = response.body;
}
After i clicked on the button to call the function PostRequest() and send the object to internet i got a strange message and the call is not done:
======== Exception caught by gesture ===============================================================
The following assertion was thrown while handling a gesture:
Scaffold.of() called with a context that does not contain a Scaffold.
No Scaffold ancestor could be found starting from the context that was passed to Scaffold.of(). This usually happens when the context provided is from the same StatefulWidget as that whose build function actually creates the Scaffold widget being sought.
There are several ways to avoid this problem. The simplest is to use a Builder to get a context that is "under" the Scaffold. For an example of this, please see the documentation for Scaffold.of():
https://api.flutter.dev/flutter/material/Scaffold/of.html
A more efficient solution is to split your build function into several widgets. This introduces a new context from which you can obtain the Scaffold. In this solution, you would have an outer widget that creates the Scaffold populated by instances of your new inner widgets, and then in these inner widgets you would use Scaffold.of().
A less elegant but more expedient solution is assign a GlobalKey to the Scaffold, then use the key.currentState property to obtain the ScaffoldState rather than using the Scaffold.of() function.
The context used was: CreateTeamView
state: _CreateTeamViewState#c4658
When the exception was thrown, this was the stack:
#0 Scaffold.of (package:flutter/src/material/scaffold.dart:1472:5)
#1 _CreateTeamViewState.build.<anonymous closure> (package:footyappp/Fantazyy/create_team_view.dart:325:36)
#2 _InkResponseState._handleTap (package:flutter/src/material/ink_well.dart:993:19)
#3 _InkResponseState.build.<anonymous closure> (package:flutter/src/material/ink_well.dart:1111:38)
#4 GestureRecognizer.invokeCallback (package:flutter/src/gestures/recognizer.dart:183:24)
...
Handler: "onTap"
Recognizer: TapGestureRecognizer#eeb07
debugOwner: GestureDetector
state: possible
won arena
finalPosition: Offset(187.1, 658.5)
finalLocalPosition: Offset(187.1, 25.1)
button: 1
sent tap down
====================================================================================================
Here the full code of Flutter:
import 'package:flutter/material.dart';
import 'package:footyappp/Fantazyy/club_json.dart';
import 'package:footyappp/Fantazyy/controller.dart';
import 'package:footyappp/Fantazyy/styles.dart';
import 'package:footyappp/Fantazyy/player%20copy.dart';
import 'package:footyappp/Fantazyy/players_creation_details_view.dart';
import 'package:http/http.dart';
class CreateTeamView extends StatefulWidget {
List<Playerr> selectedPlayers;
CreateTeamView({
Key key,
players,
selectedPlayers,
}) : selectedPlayers = (selectedPlayers == null) ? new List<Playerr>.generate(16, (int index) => null) : selectedPlayers;
#override
_CreateTeamViewState createState() => _CreateTeamViewState();
}
class _CreateTeamViewState extends State<CreateTeamView> {
Future <void> PostRequest() async {
// set up POST request arguments
final url = Uri.parse('http://localhost:3000/api/questions/addQuestion');
Map<String, String> headers = {"Content-type": "application/json"};
ClubJson club = ClubJson(userid: 1, name: "dsds", price: 55.2,players: null );
for(var item in widget.selectedPlayers){
club.players.add(Player(id:item.playerID,firstname:item.firstName,lastname:item.lastName,position:item.position,price:item.price,appearences:item.appearances,goals:item.goals,assists:item.assists,cleansheets:item.cleanSheets,redcards:item.redCards,yellowcards:item.yellowCards,image:item.image));
}
String json = club.toJson().toString();
print(club);
// make POST request
Response response = await post(url, headers: headers, body: json);
// check the status code for the result
int statusCode = response.statusCode;
// this API passes back the id of the new item added to the body
String body = response.body;
}
final double _checkboxHeight = 30.0;
double _startingBudget = 107.0;
double _budget = 107.0;
bool _everyTeam = false, _minThreeFreshers = false, _maxThreeSameTeam = true, _isTeamNameLong = false, _buttonEnabled = true;
String _teamName = "";
Widget _saveChanges = Text("Press to save changes");
#override
void initState() {
Map<int,int> teamCount = new Map<int, int>();
int fresherCount = 0;
for (Playerr player in widget.selectedPlayers) {
if (player != null) {
_budget -= player.price;
/* if (teamCount[player.club] == null) {
teamCount[player.teams] = 1;
} else {
teamCount[player.teams]++;
if (teamCount[player.club] > 3) _maxThreeSameTeam = false;
}*/
}
}
_minThreeFreshers = (fresherCount >= 3);
_everyTeam = (teamCount.length >=7);
super.initState();
}
emptyPlayer(int index) {
Playerr player = widget.selectedPlayers[index];
Widget playerView;
if (player == null) {
playerView = Image.asset("Assets/shirt_blank.png", fit: BoxFit.fitHeight,);
} else {
playerView = Column(
children: <Widget>[
Expanded(
child: Image.asset(player.image, fit: BoxFit.fitHeight,),
),
Container(
color: Colors.green,
child: Text(player.firstName.substring(0,1) + ". " + player.lastName, textAlign: TextAlign.center, softWrap: false, overflow: TextOverflow.fade,),
),
Container(
color: Colors.green,
child: Text("£${player.price}m", textAlign: TextAlign.center),
),
],
);
}
return Expanded(
child: InkWell(
onTap: () => Navigator.pushReplacement(context, MaterialPageRoute(builder: (BuildContext context) {return PlayersCreationDetailsView(selectedPlayers: widget.selectedPlayers, playerIndex: index,);})),
child: Padding(padding: EdgeInsets.only(left: 3.0, right: 3.0), child:playerView,)
),
);
}
#override
Widget build(BuildContext context) {
return WillPopScope(
onWillPop: () async => false,
child: Scaffold(
appBar: AppBar(title: Text("Create your team"),),
body: Stack(
children: <Widget>[
Column(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
Expanded(
child: Stack(
children: <Widget>[
Positioned.fill(
child: Image.asset("Assets/pitch.jpg", fit: BoxFit.fitWidth, alignment: Alignment.topLeft,)
)
]
)
),
],
),
Column( //players
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
Expanded(
flex: 1,
child: Container()
),
Expanded(
flex: 6,
child: Padding(
padding: EdgeInsets.only(left: 40.0, right: 40.0), child: Row(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: List.generate(2, (index) => emptyPlayer(index)),
),
)
),
Expanded(
flex: 1,
child: Container()
),
Expanded(
flex: 6,
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: List.generate(5, (index) => emptyPlayer(index+2)),
)
),
Expanded(
flex: 1,
child: Container()
),
Expanded(
flex: 6,
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: List.generate(5, (index) => emptyPlayer(index+7)),
)
),
Expanded(
flex: 1,
child: Container()
),
Expanded(
flex: 6,
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: List.generate(4, (index) => emptyPlayer(index+12)),
)
),
Expanded(
flex: 1,
child: Container()
),
Container(
color: Styles.colorAccentDark,
padding: EdgeInsets.only(left: 8.0, right: 8.0),
child: Column(
children: <Widget>[
Padding(
padding: EdgeInsets.only(top: 4.0, bottom: 4.0),
child: Row(
children: <Widget>[
Expanded(
child: Text("Remaining Budget", style: Styles.budgetLabel,),
),
Text("£${_budget}m", style: Styles.budgetLabel,)
],
),
),
Row(
children: <Widget>[
Expanded(
child: Text("At least one player from every team:", style: Styles.checkboxLabel),
),
Container(
height: _checkboxHeight,
child: Checkbox(
value: _everyTeam,
onChanged: (bool) => null,
),
)
],
),
Row(
children: <Widget>[
Expanded(
child: Text("At least two freshers:", style: Styles.checkboxLabel),
),
Container(
height: _checkboxHeight,
child: Checkbox(
value: _minThreeFreshers,
onChanged: (bool) => null,
),
)
],
),
Row(
children: <Widget>[
Expanded(
child: Text("Max three players from same team:", style: Styles.checkboxLabel),
),
Container(
height: _checkboxHeight,
child: Checkbox(
value: _maxThreeSameTeam,
onChanged: (bool) => null,
),
)
],
),
Padding(
padding: EdgeInsets.only(bottom: 4.0),
child: Row(
children: <Widget>[
Expanded(
child: TextField(
onChanged: (string) {
if (string.length >= 4) {
_teamName = string;
setState(() {
_isTeamNameLong = true;
});
} else {
setState(() {
_isTeamNameLong = false;
});
}
},
decoration: InputDecoration(
fillColor: Styles.colorBackgroundLight,
filled: true,
hintText: "Team Name",
),
)
),
Container(
height: _checkboxHeight,
child: Checkbox(
value: _isTeamNameLong,
onChanged: (bool) => null,
),
)
],
),
)
],
),
)
,
new MaterialButton(
height: 50.0,
minWidth: double.infinity,
color: Styles.colorButton,
splashColor: Colors.teal,
textColor: Colors.white,
child: _saveChanges,
onPressed: () {
if (_buttonEnabled) {
String message = "";
if (!_everyTeam) {
message +=
"You need at least one player from every team \n";
}
if (!_minThreeFreshers) {
message +=
"You need at least 3 freshers in your team \n";
}
if (!_maxThreeSameTeam) {
message +=
"You can have at most 3 players from the same team \n";
}
if (!_isTeamNameLong) {
message +=
"Your team name must be at least 4 characters long \n";
}
if (_budget < 0) {
message += "You can't exceed the budget \n";
}
if (message != "") {
final snackBar = SnackBar(
content: Text(message),
duration: Duration(seconds: 2)
);
Scaffold.of(context).showSnackBar(snackBar);
setState(() {
_saveChanges = FutureBuilder(
future: PostRequest(),
builder: (context, snapshot) {
if (snapshot.connectionState ==
ConnectionState.done) {
_buttonEnabled = true;
return Text("Press to save changes");
}
// By default, show a loading spinner and disable button
_buttonEnabled = false;
return CircularProgressIndicator();
},
);
}); }
}
}
),
],
),
],
)
)
);
}
}

Answer 1

try adding a key for scaffold widget like this
final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey();
Scaffold(
key: scaffoldKey,
body:....
scaffoldKey.currentState.showSnackBar(snackBar);
or if you are using flutter 2 use this to show SnackBar
ScaffoldMessenger.of(context).showSnackBar(snackBar)